https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86465
Bug ID: 86465
Summary: C++17 <optional> triggers: ‘<anonymous>’ may be used
uninitialized in this function
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: proski at gnu dot org
Target Milestone: ---
Created attachment 44378
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44378&action=edit
Preprocessed test case
The attached file triggers a warning:
$ g++ -std=c++17 -Wall -O2 -c optional.cpp -save-temps
optional.cpp: In member function ‘virtual std::optional<int>
Child::get_hairy_value()’:
optional.cpp:20:25: warning: ‘<anonymous>’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
return {};
^
The issue is observed with gcc 8 as packaged by Fedora
(gcc-8.1.1-1.fc28.x86_64) and with the current gcc trunk (commit
c85ec25b97e485c6f3493fc42c473db2a11ac9ea). gcc 7.3.0 doesn't exhibit the bug.
Interestingly, the preprocessed file generated by gcc 7.3.0 doesn't trigger the
warning in gcc 8 or 9.
Also, the warning goes away if experimental/optional is used, so C++17 is
required to reproduce it.
Optimization (at least -O1) is required to trigger the warning.
